Olefin metathesis has emerged as a unique and powerful transformation for the interconversion of olefinic hydrocarbons, namely due to the development of well-defined catalysts. See Grubbs, R. H. Handbook of Metathesis, Wiley-VCH: Weinheim, Germany (2003). The exceptionally wide scope of substrates and functional group tolerances makes olefin metathesis a valuable technique that quickly and efficiently produces otherwise hard to make molecules, compared to traditional synthetic organic techniques. In particular, certain Ruthenium and Osmium metal carbene compounds known as “Grubbs catalysts,” have been identified as effective catalysts for olefin metathesis reactions such as, cross metathesis (CM), ring-closing metathesis (RCM), ring-opening metathesis (ROM), ring-opening cross metathesis (ROCM), ring-opening metathesis polymerization (ROMP) and acyclic diene metathesis (ADMET) polymerization. The use of such Ruthenium carbene complexes has greatly expanded the scope of olefin metathesis due to increased tolerance of organic functionality, moisture, and oxygen.
Polymers prepared by metathesis polymerization of cyclic olefins (i.e., ROMP polymers), particularly polymers based on dicyclopentadiene, having good resistance to hydrocarbon fluids (e.g., hydrocarbon solvents such as gasoline, naphthas, chlorinated hydrocarbons, toluenes, benzenes xylenes and other aromatics) are desirable and have numerous applications in industry. Therefore, there is an ongoing need in industry for ROMP polymers having improved resistance to hydrocarbon fluids, particularly hydrocarbon solvents.
U.S. Pat. No. 4,507,453 teaches that in polymers prepared by metathesis polymerization of cyclic olefins (i.e., ROMP polymers), particularly polymers based on dicyclopentadiene, one important property that gives rise to hydrocarbon fluid resistance is the extent to which the polymer is crosslinked, where the extent of crosslinking is provided by the polymer's gel swell value. As described therein, gel swell is typically measured through methods which are in general accordance with ASTM D-3616, which sets forth a method for making gel swell measurements by immersing a polymer in a hydrocarbon solvent (e.g., toluene) for a period of time at a given temperature, where gel swell is expressed as a percentage defined as final polymer weight minus initial polymer weight, divided by initial polymer weight times one hundred.
U.S. Pat. No. 5,728,785 teaches that polymers prepared by metathesis polymerization of cyclic olefins (i.e., ROMP polymers), particularly polymers based on dicyclopentadiene, having high density crosslinking are desirable for their improved mechanical strength and low gel swell. In other words, increased crosslink density correlates to decreased gel swell.
U.S. Pat. No. 5,268,232 teaches that polymers prepared by metathesis polymerization of cyclic olefins (i.e., ROMP polymers), particularly polymers based on dicyclopentadiene, are capable of crosslinking the unsaturated double bonds of the polymer and thereby increasing the crosslink density of the polymer and its glass transition temperature (Tg). In other words, increased crosslink density correlates to increased Tg values.
Therefore, based on the teachings in the art, one skilled in the art would anticipate that ROMP polymers having higher Tg values, would correspondingly possess a higher crosslink density and also a lower gel swell. So, relying on the teachings in the art, one skilled in the art wanting to prepare a polymer having a lower gel swell, would expect such polymers to possess a higher Tg value.
The inventors have discovered that while ROMP polymers of the present invention possess comparable Tg values to ROMP polymers known and exemplified in the art, the ROMP polymers of the present invention possessed lower gel swell values than ROMP polymers known and exemplified in the art. This discovery, as described and exemplified herein, was surprising and unexpected in view of the teachings in the art.